MUTAGENS OF POTENTIAL SIGNIFICANCE 



179 



ZYGOTE 



PRIMORDIAL 

 GERM 

 CELLS 



V 9 — V 9 



STEM CELLS 



T^-^ 



X 



PERIOD 4 



SPERM CLONE 



PERIOD 



PERIOD 2 



PERIOD 3 



EARLY FETUS 



TO PUBERTY 



REPRODUCTIVE LIFE 



DAYS 



10^ 



5X10' 



10' 



Figure 25. The germ line of man. 



A schematic diagram showing the four periods of possible sensitivity to 

 mutagenic agents in the human male. The average span of a human genera- 

 tion from zygote to zygote is taken to be 30 years (approximately 10* 

 days). 



with caffeine, but those data are certainly not enough to establish 

 linearity. I shall assume it, and if anyone wants to introduce further 

 evidence on this point, I should be glad to hear it. 



Benzer: There are very good data on nitrous acid, by the Tiibingen 

 group, over a wide range of concentration (59). 



Goldstein: But that would not fall into the category I am talking 

 about, presumably, since you induce mutations in vitro. I shall assume, 

 then, that there is a mutation probability for replication in 1 M 

 mutagen and that the actual probability (p) is a definite fraction of 

 this standard probability, determined by the concentration (c) that 

 is actually present. Thus, p = poc. 



I am also going to assume that the probability of mutation per cell 

 cycle is the same at all stages of development of the germ line and 

 of the sperm. This may be entirely wrong, but if it is, corrections 

 are relatively simple to introduce. 



